1. Field of the Invention.
The invention concerns a call load sharing system between several data processing units applicable in particular to a real time data processing system such as, for example, a central control telephone or telegraph exchange, a remote control system or an analogous system.
2. Description of the Prior Art
In a central control system, a data processing central unit which is generally a stored program computer controls the operation at the different exchange signalling and switching units. For this purpose, it interrogates them at regular time intervals by means of scanners in order to detect all remarkable events. It processes the information thus obtained, and according to the provided operation, updates the information that it knows concerning the exchange situation, or controls appropriate operations by sending orders corresponding to the exchange signalling and switching units.
At least two central units are provided, sufficiently powerful so that in case of failure of one of them, the other takes over all the tasks to be performed. The scanners and the order drivers are common to both central units which alternately use them according to the needs. In a normal state, that is in the absence of defect, several operating modes can be contemplated. In the "normal-reserve" operation, one single central unit insures the processing of all calls, the other central unit being ready to intervene in case of failure of the first one. In the "call load sharing" operation, each central unit takes in charge one part of the traffic and processes totally the calls handled by it.